Modern electronic technology continues to provide consumers with an ever expanding variety of miniature or portable electronic devices. Examples of these devices include communications devices such as portable cellular telephones, pocket pagers or radio transceivers as well as entertainment devices such as portable AM/FM radios or tape players. Because these devices are intended for around the clock use, various switches and displays must be illuminated to permit equipment operation at night or in poorly illuminated areas.
Miniature incandescent bulbs have been and continue to be a relatively reliable and cost effective method of illuminating displays or controls needed for the operation of portable electronic equipment. Because most portable equipment is battery powered, the miniature bulbs are usually low voltage, direct current devices powered directly or indirectly by the equipment batteries.
The portable nature of modern electronic equipment subjects miniature incandescent bulbs to shocks and vibrations which tend to reduce the effective life of miniature incandescent bulbs below the finite life expectancy inherently associated with miniature incandescent devices. Therefore, portable electronic equipment is typically manufactured in such a manner as to permit easy bulb replacement. One bulb configuration permitting easy bulb replaceability is a miniature surface mount bulb in which a generally elongated bulb envelope includes a metal end cap at each end of the bulb envelope. The end caps are designed to be tensionably or otherwise retained by a pair of complementary socket elements or solder terminals which provide an electrical connection between the bulb filament and the bulb socket elements or solder terminals.
While various designs for miniature incandescent bulbs are known, many of these designs are relatively expensive and cumbersome to manufacture. For example, prior art devices such as those illustrated in U.S. Pat. No. 4,952,838 to DuNah teach lamp structure having open metal end caps through which the bulb filament must be threaded prior to soldering or otherwise electrically securing the filament to the metal end caps. Other miniature lamp designs utilize an end cap having a small hole at the end through which the filament must be threaded, which is even more difficult to assemble than for the lamp of DuNah. Manipulative steps such as this tend to increase bulb costs, thereby leading to higher equipment prices or a reduction in the use of bulbs from what could otherwise be afforded if a cheaper miniature surface mount lamp device was available. Accordingly, a need exists for a miniature surface mount lamp that can be constructed more easily and inexpensively.